The hunt for pieces of Mercury on Earth

With the distant planet Mercury visible in the evening sky this week, it's worth looking at new research that suggests pieces of the hot planet are waiting to be found right here on Earth.

We know that pieces of the Moon, Mars and asteroids have been found as meteoritic rock fragments on Earth. A recent computer model of Mercury's creation billions of years ago shows us that some of its ejected rock and dust ended up falling on Earth and Venus.

These complex computer simulations, produced by scientists at the University of Bern, Switzerland, tracked where Mercury's ejecta travelled over the course of millions of years.

The Bern scientists spent months speculating about the fate of material blasted off Mercury and out into space. More simulations resulted and the Bern team now thinks that a large proto-Mercury collided with a giant asteroid about 4.5 billion years ago.

Mercury is a dense planet, which implies that it contains lots of heavy metals. Mercury was formed much like Earth's Moon by a titanic collision of celestial bodies; it then reaccreted, into the planet we know today, following the impact.

At the end of the first Bern simulations, a dense metal and rock body remained after the impact with streams of rapidly escaping debris. A second simulation tracked the ejected matter until it either landed on nearby planets, was thrown into deep space, or simply fell into the Sun's deep gravity well.

Simulations showed that some of the ejected Mercury material reached all the way to Venus and Earth. Such computer simulations, made by pioneering researchers such as NASA's Dean Chapman, began in earnest during the 1960s. These simulations have shown how ejecta from the Moon and Mars can reach Earth. In fact, Mars meteorites and some lunar material have been identified on Earth; however researchers still bicker over the origins of some of the space rocks.

Bern scientists stuck their collective necks out and suggested that Earth might be the resting ground to as much as 16 quadrillion tons of Mercury's ejected rock-wow, that's a lot of Mercury on Mother Earth. However, this idea will remain a scientific challenge to prove, at least until geological samples from Mercury's surface are collected and returned to Earth for study. Next, the rocks have to be chemically matched alongside suspected Mercurian meteorites to ultimately prove theory as fact.

What's in the Sky-Get a fleeting glimpse of the planet Mercury low in the western sky around 8 p.m., Saturday, Aug. 22 (see accompanying sky map).

Louis Varricchio, M.Sc., lives in Vermont. He is a former NASA senior science writer and a current member of the NASA/JPL Solar System Ambassador program. He is also a member of the Association of Lunar and Planetary Observers.